Re: [PATCH 2/2] sched: mark PRINTK_DEFERRED_CONTEXT_MASK in __schedule()

[Peter Zijlstra]

On Mon, Sep 28, 2020 at 12:52:44AM -0700, Joe Perches wrote:
> On Mon, 2020-09-28 at 09:32 +0200, Peter Zijlstra wrote:
> > On Mon, Sep 28, 2020 at 12:11:30AM +0800, Chengming Zhou wrote:
> > > The WARN_ON/WARN_ON_ONCE with rq lock held in __schedule() should be
> > > deferred by marking the PRINTK_DEFERRED_CONTEXT_MASK, or will cause
> > > deadlock on rq lock in the printk path.
> []
> > NAK printk_deferred is an abomination, kill that.
> 
> Didn't you introduce it?
> Should you be complaining to yourself?

Yeah. I should've hacked around it then I suppose. Still, no reason to
proliferate that crap. Afaik the new printk should be able to deal with
this at some point.

The thing we're not going to do it add a cache-miss to schedule just
because.